From 3fb91566bb9978b51e2b382df408da5dcd76cccb Mon Sep 17 00:00:00 2001
From: Tom Alexander <tom@fizz.buzz>
Date: Sun, 7 Jun 2020 14:45:32 -0400
Subject: [PATCH] Implement get and tap functions.

---
 src/parser/parser.rs                | 15 +++++++++
 src/renderer/inline_partial_tree.rs | 30 ++++++++++++++++++
 src/renderer/renderer.rs            | 47 +++++++++++++++++++++++++++++
 3 files changed, 92 insertions(+)

diff --git a/src/parser/parser.rs b/src/parser/parser.rs
index a671bbc..e965976 100644
--- a/src/parser/parser.rs
+++ b/src/parser/parser.rs
@@ -41,6 +41,9 @@ pub enum DustTag<'a> {
     DTHelperLessThan(ParameterizedBlock<'a>),
     DTHelperGreaterThanOrEquals(ParameterizedBlock<'a>),
     DTHelperLessThanOrEquals(ParameterizedBlock<'a>),
+    DTHelperSep(ParameterizedBlock<'a>),
+    DTHelperFirst(ParameterizedBlock<'a>),
+    DTHelperLast(ParameterizedBlock<'a>),
 }
 
 #[derive(Clone, Debug, PartialEq)]
@@ -240,6 +243,18 @@ fn dust_tag(i: &str) -> IResult<&str, DustTag> {
             parameterized_block("{@", &tag_to_path("lt")),
             DustTag::DTHelperLessThan,
         ),
+        map(
+            parameterized_block("{@", &tag_to_path("sep")),
+            DustTag::DTHelperSep,
+        ),
+        map(
+            parameterized_block("{@", &tag_to_path("first")),
+            DustTag::DTHelperFirst,
+        ),
+        map(
+            parameterized_block("{@", &tag_to_path("last")),
+            DustTag::DTHelperLast,
+        ),
     ))(i)
 }
 
diff --git a/src/renderer/inline_partial_tree.rs b/src/renderer/inline_partial_tree.rs
index aa5779c..132c1d2 100644
--- a/src/renderer/inline_partial_tree.rs
+++ b/src/renderer/inline_partial_tree.rs
@@ -160,5 +160,35 @@ fn extract_inline_partials_from_tag<'a, 'b>(
                 Some(body) => extract_inline_partials_from_body(blocks, &body),
             };
         }
+        DustTag::DTHelperSep(parameterized_block) => {
+            match &parameterized_block.contents {
+                None => (),
+                Some(body) => extract_inline_partials_from_body(blocks, &body),
+            };
+            match &parameterized_block.else_contents {
+                None => (),
+                Some(body) => extract_inline_partials_from_body(blocks, &body),
+            };
+        }
+        DustTag::DTHelperFirst(parameterized_block) => {
+            match &parameterized_block.contents {
+                None => (),
+                Some(body) => extract_inline_partials_from_body(blocks, &body),
+            };
+            match &parameterized_block.else_contents {
+                None => (),
+                Some(body) => extract_inline_partials_from_body(blocks, &body),
+            };
+        }
+        DustTag::DTHelperLast(parameterized_block) => {
+            match &parameterized_block.contents {
+                None => (),
+                Some(body) => extract_inline_partials_from_body(blocks, &body),
+            };
+            match &parameterized_block.else_contents {
+                None => (),
+                Some(body) => extract_inline_partials_from_body(blocks, &body),
+            };
+        }
     }
 }
diff --git a/src/renderer/renderer.rs b/src/renderer/renderer.rs
index d1ca186..dd0699b 100644
--- a/src/renderer/renderer.rs
+++ b/src/renderer/renderer.rs
@@ -20,6 +20,7 @@ use crate::renderer::inline_partial_tree::InlinePartialTreeElement;
 use crate::renderer::iteration_context::IterationContext;
 use crate::renderer::parameters_context::ParametersContext;
 use crate::renderer::walking::walk_path;
+use std::borrow::Borrow;
 use std::collections::HashMap;
 
 #[derive(Clone, Debug)]
@@ -644,11 +645,57 @@ impl<'a> DustRenderer<'a> {
                     }
                 }
             }
+            DustTag::DTHelperSep(parameterized_block) => {}
+            DustTag::DTHelperFirst(parameterized_block) => {}
+            DustTag::DTHelperLast(parameterized_block) => {}
         }
 
         Ok("".to_owned())
     }
 
+    /// Read a value from the context tree
+    pub fn get<P>(
+        &'a self,
+        breadcrumbs: &'a Vec<BreadcrumbTreeElement<'a>>,
+        name: &Vec<P>,
+    ) -> Result<IceResult<'a>, WalkError>
+    where
+        P: Borrow<str>,
+    {
+        let val =
+            walk_path(breadcrumbs, name).map(|ice| ice.into_context_element(self, breadcrumbs));
+        match val {
+            Ok(Some(ice_result)) => Ok(ice_result),
+            Ok(None) => Err(WalkError::CantWalk),
+            Err(walk_error) => Err(walk_error),
+        }
+    }
+
+    /// Read a value from the parameters context
+    ///
+    /// Returns None if the key is not present at all
+    pub fn tap<P>(
+        &'a self,
+        breadcrumbs: &'a Vec<BreadcrumbTreeElement<'a>>,
+        parameters: &'a ParametersContext<'a>,
+        name: &P,
+    ) -> Option<Result<IceResult<'a>, WalkError>>
+    where
+        P: Borrow<str>,
+    {
+        if !parameters.contains_key(name.borrow()) {
+            return None;
+        }
+        let val = parameters
+            .walk("key")
+            .map(|ice| ice.into_context_element(self, breadcrumbs));
+        match val {
+            Ok(Some(ice_result)) => Some(Ok(ice_result)),
+            Ok(None) => Some(Err(WalkError::CantWalk)),
+            Err(walk_error) => Some(Err(walk_error)),
+        }
+    }
+
     fn new_breadcrumbs_section<'b>(
         &'b self,
         breadcrumbs: &'b Vec<BreadcrumbTreeElement<'b>>,